Okay, I've been scouring the net for info about this game, and there really doesn't seem to be much out there.

What I've learned: The more runes you consume, have in your inventory, or have in your stash, decreases your rune drop rate. I've also heard that learning more combat arts decreases the drop rate (for example having consumed 40 runes for one skill would leave you with a higher rate than consuming 20 runes each for two different skills.)

What I'd like to know: Specific formulas on how using or hoarding runes actually does affect your rune drop rate. Most of the info I've found has been at the official Sacred forum, which doesn't allow the discussion of glitches, bringing me to my next issue.

Apparently there was at some point in some version of this game something called the "symoe runateknik glitch." I have no idea if I'm spelling that correctly, but it had something to do with the combo master and using 8 runes to get a rune of your choice while preserving possession of the original 8 runes, basically giving you an unlimited supply of runes. The only whisperings I've found about this mysterious glitch have been on the official Sacred forums, and the handful of posts that mention it generally link to the now-defunct Ascaron forums. I've messed around a bunch in the combo master, but haven't figured out anything useful. Anyone ever heard of this? Is it real? Do you know how to do it? Does it work in Sacred Gold?

Okay, I just figured it out. The rune glitch I talked about in my above post works in Sacred Gold.

When I did it, I had 8 runes in my inventory and nothing else...not sure if having other items in inventory would mess it up.

It's pretty easy to do. With 8 runes in your inventory, quicksave (F9) right in front of the combo master (make sure your inventory is CLOSED when you save.) Then talk to the combo master and put two of your runes up in the slots to make a random rune. Set that rune aside in your inventory. Do this 3 more times with your other 6 original runes. Now put all 4 of the new runes you've created up in the green combomaster slots. Quickload (F8) and when you talk the the combo master and go to the rune exchange screen, you'll see that you have your 8 original runes, but the 4 that you created are still up in the green slots! You can try to grab them, but the game won't let you put them in your inventory. However, it WILL let you exchange them for a rune of your choice.

Pretty sweet if you're the kind of person who doesn't mind using glitches. My plan is to play through the game normally and only use this if the runes stop dropping and my character is under powered. Glad I found, it though!

Edit: I'm still interested in the rune drop rate formulas if anyone has any ideas about that.

A huge necro but just confirming that this still works. Tying rune drop rates in the first game to stuff like how many runes you have in inventory, how many runes you've learned in total, how many CAs you have unlocked in total and lowering the drop rate as you play the game was beyond stupid.

Read here for details:
http://pctalk.info/Games/Sacred2/Wolfes.Lair/SacredUnderworld/Pages/GameBasics-RunesandItems.html

This glitch gives me the peace of mind in case runes stop dropping, so thanks (9 years later :P) for laying out how to do it.

EDIT:
Just now, I'm going to resort to this. Currently at level 135 in Niobium and runes pretty much stopped dropping. The only reliable way to get runes is just spam farming quests over and over or rolling a low level char and giving all the runes it finds to the late game one. I could currently use like 100 more Heroic Courage runes and 50+ of Dagger Stare, with about 10 or so of Hard Hit and Multi Hit. Getting them normally would take days if not more of mind numbing tedium. This way, I can get them in a couple of hours.

Spam farming quests over and over would get extremely boring very quickly and you have to save before every quest turn-in and spam load until they give you the one you want. Having to play a different, low level char just to progress your main one is just bad, so this glitch is indeed a life saver. You can make about 2 runes per minute this way, depending on your speed and precision with the mouse.

There would be no need to resort to this if runes just had a fixed drop rate like they do in Sacred 2, but alas...

You have to do it exactly as stated in the post above. Get 8 runes, quick save in front of Combo Master use 4 pairs to create random runes, put those random runes into the slots and quick load. Result is all 8 runes still present and the ability to mix a rune of your choice. Repeat as many times as needed.